Searching for New Exotic Physics at the LHC a.k.a. Searches Beyond Supersymmetry Dave Charlton University of Birmingham Before, Behind and Beyond the Discovery of the Higgs Boson Royal Society, 20-21 January 2014

Menu Why search for exotic physics? Simple event types – “bump hunting” Top as a probe Long-lived particles Dark matter Conclusions

Simple Event Types “Bump Hunting”

m(ee)=1.54 TeV

m(μ+μ−)=1.82 TeV

Dilepton resonances Model Mass limit (95% CL) Z'SSM 2.96 TeV Z'(ψ) 2.60 TeV Z'SSM 2.86 TeV Z'(E6 models) 2.38-2.54 TeV G*(k/MPl=0.1) 2.47 TeV CMS ATLAS excluded Convert to lower mass limits for specific models In these models, mass of a new resonance must be more than 2-3 TeV Upper limits placed on rate of events (cross-section times branching ratio σ∙B(X→ℓℓ) at 95%CL) ATLAS-CONF-2013-073 Next step: 13 TeV LHC operation – mass reach will ~double

High-mass eeγ event

W' decaying to leptons Simplest case: W' → ℓν Single high-pT lepton and Etmiss Again, no excess above backgrounds observed Combining e,μ channels, SM-like W' excluded by CMS for m(W') > 3.35 TeV (95% CL) CMS PAS EXO-12-060

Event selected in the W'→ℓν analysis, with mT=2.3 TeV

Searches in dijets CMS PAS EXO-12-059 Inclusive dijet mass spectrum – extends up to 5 TeV! Fit with smooth function, look for resonances Limits on many models: string resonances, excited quarks, axigluons, colorons, s8 resonances, E6 diquarks, W' and Z' bosons, and Randall-Sundrum gravitons, up to 5 TeV 5 TeV Further searches in: dijet final states, look at angular distributions in the detector, look at b-tagged jets; multijet topologies searching for 3-jet resonances … …

Top as a Probe

High transverse momentum top quarks b W− q q′ jet t b W− q q′ jet High transverse momentum top quarks Low pT Common experimental challenge for searches for heavy particles decaying to top quarks – identification of high-pT tops At high-pT, the top decay products can merge into a single “fat” jet t merged jet High pT Sophisticated “jet substructure” techniques to identify these

Search for X → tt Search for a heavy particle decaying to tt Both semileptonic (tt → bℓvbqq') and hadronic (tt → bqq'bq''q''') decays Search both for resolved and merged jets → extend to very high momentum top quarks ATLAS-CONF-2013-052 Phys Rev Lett 111 (2013) 211804

Candidate tt event with m(tt)=2.6 TeV

New heavy quarks (“vector-like”) New heavy quarks (T, B): decay modes T → bW, T → tZ, T → tH B → bZ, B → tW, (B → bH) arXiv:1311.7667 Several event signatures: Single lepton plus jets/ETmiss Same- and opposite-sign dileptons plus jets/ETmiss Trileptons plus jets/ETmiss Use b-tagging to improve signal/background Specially constructed discriminant

Put all the information together – complex multidimensional exclusion Vector-like quarks Put all the information together – complex multidimensional exclusion

Combining all channels analysed, CMS obtain lower mass limits of Vector-like quarks Combining all channels analysed, CMS obtain lower mass limits of m(T) > 690-782 GeV (95% CL) m(B) > 520-785 GeV (95% CL) CMS PAS B2G-13-003 arXiv:1311.7667

Long-lived Particles

Dark Matter

TeV TeV